Background: A better understanding of the environmental factors leading to inflammatory bowel disease
should help to prevent occurrence of the disease and its relapses.
Aim: To review current knowledge on dietary risk factors for inflammatory bowel disease.
Methods: The PubMed, Medline and Cochrane Library were searched for studies on diet and risk of
inflammatory bowel disease.
Results: Established non-diet risk factors include family predisposition, smoking, appendectomy, and
antibiotics. Retrospective case–control studies are encumbered with methodological problems. Prospective
studies on European cohorts, mainly including middle-aged adults, suggest that a diet high in protein
from meat and fish is associated with a higher risk of inflammatory bowel disease. Intake of the n-6
polyunsaturated fatty acid linoleic acid may confer risk of ulcerative colitis, whereas n-3 polyunsaturated
fatty acids may be protective. No effect was found of intake of dietary fibres, sugar, macronutrients,
total energy, vitamin C, D, E, Carotene, or Retinol (vitamin A) on risk of ulcerative colitis. No prospective
data was found on risk related to intake of fruits, vegetables or food microparticles (titanium dioxide and
aluminium silicate).
Conclusions: A diet high in protein, particular animal protein, may be associated with increased risk of
inflammatory bowel disease and relapses. N-6 polyunsaturated fatty acids may predispose to ulcerative
colitis whilst n-3 polyunsaturated fatty acid may protect. These results should be confirmed in other
countries and in younger subjects before dietary counselling is recommended in high risk subjects.